Blood sampling device

ABSTRACT

A blood sampling device has a lancet ( 2 ) captive within a housing ( 1 ), to be released from a rearward primed position by pressing a trigger ( 18 ) on the side of the housing. A spring ( 3 ) shoots the lancet ( 2 ) forwards, momentarily to project its tip. The lancet ( 2 ) is initially held by a hooked tongue ( 25, 28 ) that latches behind a transverse web ( 10, 11 ) within the housing, the trigger action dislodging that engagement. The tongue ( 25 ) either springs back after release and so will abut the trigger ( 18 ) or the front of the web ( 10 ) if pushed back in an attempt to re-latch, or it will stay permanently deformed and thus be unable to re-engage the web ( 10 ). Alternatively, the trigger ( 18 ) may slice off the hook ( 28 ), making re-use impossible.

BACKGROUND OF THE INVENTION

This invention relates to blood sampling devices.

DESCRIPTION OF THE RELATED ART

A common form of blood sampling device is a skin pricker comprising aspring loaded lancet in a small plastics housing with a triggermechanism to release the lancet. Some require the lancet to be cocked orprimed before being released, while others are assembled and sold in thecocked condition, ready to fire. But they are all quite simple andcheap, and can be thrown away after a single use.

A standard feature is that the lancet springs back a sufficient distanceto retract the needle tip inside the housing after that tip hasmomentarily projected. Whilst that can give protection againstsubsequent injury, various measures have been devised to try to ensurethat the user cannot reset the device and fire it again. This hascertainly been made difficult, but the ideal is to make it impossible.

One solution to this has been proposed in EP-B-0 582 226, where thelancet has wings that initially rest against internal shoulders of thefiring device, holding the lancet back against a drive spring. A pushbutton at the rear end is pressed to force the wings to break off orfold back, allowing the drive spring to act and urge the lancetforwards. If the wings fold, as shown in FIG. 2 of the Patent, they willdrag against the inside of the barrel of the firing device and impederetraction. In any event it is deemed necessary to provide a returnspring. Also, the push button action and the radially projecting wingscombine to require the rear end of the barrel to be rather bulky, firstto provide the internal shoulders and secondly to provide externalshoulders affording a grip for the user against the forward pressure ofthe push button. So it is not particularly compact and it requires aconsiderable number of components (barrel, two springs, push button andlancet) to be assembled.

SUMMARY OF THE INVENTION

It is the aim of this invention to provide a sleeker, non-reusabledevice with fewer components.

According to the present invention there is provided a blood samplingdevice comprising a barrel containing a spring-loaded lancet releasableby a trigger from a primed rearward position, momentarily to project itstip from the forward end of the barrel, the lancet having a distortableor detachable appendage to engage the barrel and hold the lancet againsta drive spring, characterised in that the appendage extends rearwardlyfrom the lancet and latches to a detent provided by the internalstructure of the barrel, and in that the release of the lancet is by atrigger integral with the barrel being pressed in transversely to thebarrel to unlatch the appendage.

Conveniently, the housing is an integral moulding with two halves hingedtogether to encase the lancet and a spring. Preferably, the trigger isan elongate element springing outwardly and rearwardly from one half ofthe barrel and with a rear end portion capable of projecting in throughan aperture in the barrel to co-operate with the appendage. Whenactuated, the trigger may have a snap engagement with the barrel toretain it in its actuated position. This serves both as an indicationthat the device has been used and as a back-up for the non-recockingfeature.

The appendage may have resilient flexure so that, after clearing thedetent and trigger, it resumes its original position and will engage aportion of the retained trigger forward of the detent if the lancet isurged back towards its primed position. In the absence of any priorobstruction by the trigger, the latch can engage the forward side of thedetent. Alternatively the appendage may have a weakness at its rootcausing it to stay bent after clearing the detent, so that if the lancetis urged back to its primed position, the appendage will not re-latch tothe detent.

The detent is conveniently formed by two transverse webs which, when thehalves are brought together, form an aperture through which theappendage extends. A finger may then project back parallel to theappendage from the rear end of the lancet and engage the edge of theaperture remote from the trigger, thereby ensuring that, when thetrigger is pressed in, the lancet is maintained in its proper alignment.

In an alternative arrangement the rear end of the appendage has a narrowneck and a head which engages behind the detent over which the necklies, and the trigger has a portion formed as a blade which initiallyregisters with the neck and, when the trigger is pressed in, severs theneck to cause the head to fall free and the lancet to be sprungforwards.

The spring will generally be a helical spring that surrounds and isconnected to the lancet, acts between the forward end thereof and anabutment forward of the detent, and extends beyond its relaxed statewhen driving the lancet forwards so that it withdraws the lancet tipinto the barrel after the momentary projection. It is thus well clear ofthe part of the lancet that co-operates with the detent and does notwill not interfere with the latching arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, some embodiments will nowbe described, by way of example, with reference to the accompanyingdrawings, in which:

FIG. 1 is a longitudinal section of a finger pricker in its pre-use or“as sold” condition,

FIG. 2 is a cross-section on the line II—II of FIG. 1,

FIG. 3 is a plan view of the pricker,

FIG. 4 is a longitudinal section of the pricker at the point of firing,

FIG. 5 is a longitudinal section of the pricker at the moment of skinpenetration,

FIG. 6 is a longitudinal section of the pricker after use,

FIG. 7 is a longitudinal section of the pricker after use and with itslancet retracted in an attempt to re-set, and

FIG. 8 is a detail, in longitudinal section, of another finger prickerin its primed condition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The pricker comprises an elongate box-like housing 1 containing a lancet2 and a spring 3, the tip 4 of the lancet needle initially beingconcealed within the rear end of an elongate cap 5 integrally mouldedwith the body 6 of the lancet. The housing 1 is also integrally mouldedin two side-by-side channel-like upper and lower halves 7 and 8 with athin web or a set of webs bridging adjacent sides and forming a hinge.These halves are subsequently folded together and adhered or welded toencase the lancet 2 and the spring 3. The rear end of the housing 1 isclosed, but the forward ends of the halves 7 and 8 have semi-circularcut-outs which combine to form an aperture 9 through which the cap 5extends.

A short distance forward from the rear end, the halves 7 and 8 havetransverse webs 10 and 11 respectively. The web 10 is actually twoseparate portions, symmetrically opposed to form an inverted T-shapedgap 12, while the web 11 has a central cut-out 13 in its free edge. Atabout the mid-length of the housing 1 there are two further transversewebs 14 and 15 which are slightly staggered and stand marginally proudof their respective halves. When the halves 7 and 8 are closed together,the webs 14 and 15 overlap, but they have cut-outs at their free edgeswhich combine to form a cruciform aperture, complementary to thecross-section of the lancet, which passes non-rotatably through thataperture. Opposed pairs of ribs 16 extend within each half from theleading end almost to the webs 14 and 15, providing grooves in whichfingers of an enlarged head 17 of the lancet are guided. The spring 3coils around the lancet and acts between this head 12, to which it iscaptive, and the webs 14 and 15.

A trigger 18 is formed as a tongue integral with the upper half 7. Awide portion 19 slopes outwardly and rearwardly from just behind webs 14and at its end narrows immediately in front of the two-part web 10 intoa central knife-like finger 20 angling back towards the housing. Theupper side of the portion 19 has a finger pad 21. The formation of thetrigger 18 leaves a generally rectangular aperture 22 spanned by the web10 with the stem of whose T-shaped gap 12 the finger 20 registers. Theplastics material of which the housing is moulded allows the trigger tobe flexed in to project the finger 20 further into the gap 12 from theposition shown in FIG. 1. On either side of the exposed mouth of the gap12 the top edge of the web 10 has forward projecting lugs 23 which cansnap over the free rear end of the portion 19 either side of the finger20 when the trigger 18 is fully depressed, thereby retaining the triggerin that position after use. This is a further measure against re-use,beyond those described below, as well as a simple visual indication ofthe state of the device.

A finger 24 and a tongue 25 project rearwardly from the rear end of thelancet, the finger 24 being straight and the tongue 25 being L-shapedand thus having an outward undercut hook 26, forming a latch. This hook26 is wider than the stem of the gap 12. Initially, the finger 24extends through the cut-out 13 and the hook 26 is caught behind cornersof the divided web 10 which are locally shaped to match the slopingundercut of the hook 26 and thus provide positive engagement whichretains the lancet 2 in a rearward position with the spring 3compressed.

The finger pricker is assembled, packaged and sold in this condition.For use, the cap 5 is twisted and pulled, to remove it as shown in FIG.4. The lancet is non-rotatable, as mentioned above, and is trapped in arearward position by the hook 26. The forward end of the housing 1 isthen applied to a finger and pressure is applied to the pad 21 of thetrigger 18. The finger 20 meets the top of the hook 26 and bends thetongue 25 so that the hook 26 is disengaged with a snap (because of theundercut) from the web 10 and has a clear forward passage through thecrossbar of the inverted T-shaped gap 12. The finger 24 may bend a bitas rather exaggeratedly shown in FIG. 4. However, the friction of thetip of the finger 20 on the hook 26 and that between the finger 24 andthe web 11 is not sufficient to hold the lancet against the spring 3,and therefore the lancet is shot forwards, briefly to project the needletip 4, as shown in FIG. 5. The lancet rebounds to the FIG. 6 position.Meanwhile, the trigger 18 is trapped in its depressed condition by thelugs 23.

If someone tries to re-cock the device by pushing the lancet back by apoking implement through the aperture 9, the lancet will be arrested bythe outside of the hook 26 coming up against the forward edge of thefinger 20, as shown in FIG. 7. There is back-up to this, and even if thetrigger was released the hook 26 would then meet the corners of the web10 that previously retained it in the primed or cocked position. Thehook 26 will still not be able to pass through the gap 12.

That assumes that the tongue 25 is resilient and resumes its originalattitude as soon as it has cleared the gap 12 on being fired.

However it is possible to make the tongue 25 with a weakness and/or of amaterial such that, once bent to the position of FIG. 4 it remains thereand does not recover. Then, although the lancet can be pressed furtherback after firing, with the trigger 18 sprung out to its initialposition and the finger 24 and tongue 25 projecting through the cut-out13 and gap 12, the hook 26 will not catch again, and as the pokingimplement is removed, the lancet will move forwards again to theposition of FIG. 6.

Instead of bending or deforming the tongue 25, an alternative way ofensuring no re-use is shown in FIG. 8. At its rear end the lancet bodynarrows at a neck 27 and terminates in a head 28 that hooks behind theperiphery of the cut-out 13 in the web 11. The web 11 is thicker than inthe previous embodiment, its front face being level with that of the web10 but with its rear face further back. The neck 27 is just to the rearof the web 10, and the trigger finger 18 terminates a transverseguillotine blade, also just to the rear of the web 10.

Pressing in the trigger slices off the head 27, the web 11 acting as anexecutioner's block. The head remains captive behind the webs 10 and 11while the lancet projects forward and rebounds as described above. Itwill be appreciated that there is no way of re-capturing the lancet inits primed condition and re-firing it.

What is claimed is:
 1. A blood sampling device comprising a barrelcontaining a spring-loaded lancet releasable by a trigger from a primedrearward position, momentarily to project its tip from the forward endof the barrel, the lancet having a distortable or detachable appendageto engage the barrel and hold the lancet against a drive spring,wherein, the appendage extends rearwardly from the lancet and latches toa detent provided by the internal structure of the barrel, the releaseof the lancet is by the trigger integral with the barrel being pressedin transversely to the barrel to unlatch the appendage, and the barrelis an integral molding with two halves hinged together to encase thelancet and the spring.
 2. A blood sampling device as claimed in claim 1,wherein the trigger is an elongate element springing outwardly andrearwardly from one half of the barrel and with a rear end portioncapable of projecting in through an aperture in the barrel to co-operatewith the appendage.
 3. A blood sampling device as claimed in claim 1,wherein the trigger, when actuated, has a snap engagement with thebarrel to retain it in its actuated position.
 4. A blood sampling deviceas claimed in claim 1, wherein the appendage has resilient flexure sothat, after clearing the detent and trigger, it resumes its originalposition and will engage a portion of the trigger, in a retainedposition, forward of the detent if the lancet is urged back towards itsprimed position.
 5. A blood sampling device as claimed in claim 1,wherein the appendage has resilient flexure so that, after clearing thedetent, it resumes its original position and, in the absence of anyprior obstruction by the trigger, will engage the forward side of thedetent if the lancet is urged back towards its primed position.
 6. Ablood sampling device as claimed in claim 1, wherein the appendage has aweakness at its root causing it to stay bent after clearing the detent,so that if the lancet is urged back to its primed position, theappendage will not re-latch to the detent.
 7. A blood sampling device asclaimed in claim 1, wherein the detent is formed by two transverse websin respective halves which, when the halves are brought together, forman aperture through which the appendage extends.
 8. A blood samplingdevice as claimed in claim 7, wherein a finger projects back parallel tothe appendage from the rear end of the lancet and engages the edge ofthe aperture remote from the trigger, thereby ensuring that, when thetrigger is pressed in, the lancet is maintained in its proper alignment.9. A blood sampling device as claimed in claim 1, wherein the appendagehas a narrow neck and a head which engages behind the detent over whichthe neck lies, and wherein the trigger has a portion formed as a bladewhich initially registers with the neck and, when the trigger is pressedin, severs the neck to cause the head to fall free and the lancet to besprung forwards.
 10. A blood sampling device as claimed in claim 1,wherein the spring is a helical spring that surrounds and is connectedto the lancet, acts between the forward end thereof and an abutmentforward of the detent, and extends beyond its relaxed state when drivingthe lancet forwards so that it withdraws the lancet tip into the barrelafter the momentary projection.
 11. A blood sampling device comprising abarrel containing a spring-loaded lancet releasable by a trigger from aprimed rearward position, momentarily to project its tip from theforward end of the barrel, the lancet having a distortable or detachableappendage to engage the barrel and hold the lancet against a drivespring, wherein, the appendage extends rearwardly from the lancet andlatches to a detent provided by the internal structure of the barrel,the release of the lancet is by the trigger integral with the barrelbeing pressed in transversely to the barrel to unlatch the appendage,and the trigger, when actuated, has a snap engagement with the barrel toretain the trigger in its actuated position against subsequentreactivation.
 12. A blood sampling device comprising a barrel containinga spring-loaded lancet releasable by a trigger from a primed rearwardposition, momentarily to project its tip from the forward end of thebarrel, the lancet having a distortable or detachable appendage toengage the barrel and hold the lancet against a drive spring, wherein,the appendage extends rearwardly from the lancet and latches to a detentprovided by the internal structure of the barrel, the release of thelancet is by the trigger integral with the barrel being pressed intransversely to the barrel to unlatch the appendage, and the appendagehas resilient flexure so that, after clearing the detent and trigger,the appedage resumes its original position and will engage a portion ofthe trigger forward of the detent if the lancet is urged back towardsits primed position.
 13. A blood sampling device comprising a barrelcontaining a spring-loaded lancet releasable by a trigger from a primedrearward position, momentarily to project its tip from the forward endof the barrel, the lancet having a distortable or detachable appendageto engage the barrel and hold the lancet against a drive spring,wherein, the appendage extends rearwardly from the lancet and latches toa detent provided by the internal structure of the barrel, the releaseof the lancet is by the trigger integral with the barrel being pressedin transversely to the barrel to unlatch the appendage, and theappendage has resilient flexure so that, after clearing the detent, theappendages resumes its original position and, in the absence of anyprior obstruction by the trigger, will engage the forward side of thedetent if the lancet is urged back towards its primed position so thatit cannot be reprimed.
 14. A blood sampling device comprising a barrelcontaining a spring-loaded lancet releasable by a trigger from a primedrearward position, momentarily to project its tip from the forward endof the barrel, the lancet having a distortable or detachable appendageto engage the barrel and hold the lancet against a drive spring,wherein, the appendage extends rearwardly from the lancet and latches toa detent provided by the internal structure of the barrel, the releaseof the lancet is by the trigger integral with the barrel being pressedin transversely to the barrel to unlatch the appendage, and theappendage has a weakness at its root causing appendage to stay bentafter clearing the detent, so that if the lancet is urged back to itsprimed position, the appendage will not re-latch to the detent.
 15. Ablood sampling device comprising a barrel containing a spring-loadedlancet releasable by a trigger from a primed rearward position,momentarily to project its tip from the forward end of the barrel, thelancet having a distortable or detachable appendage to engage the barreland hold the lancet against a drive spring, wherein, the appendageextends rearwardly from the lancet and latches to a detent provided bythe internal structure of the barrel, the release of the lancet is bythe trigger integral with the barrel being pressed in transversely tothe barrel to unlatch the appendage, the appendage has a narrow neck anda head which engages behind the detent over which the neck lies, and thetrigger has a portion formed as a blade which initially registers withthe neck and, when the trigger is pressed in, severs the neck to causethe head to fall free and the lancet to be sprung forwards.